A university student spends his summer months in his home town, where he works for a local microbrewery during the evening hours. In the late morning, he attends the local community college, where he takes summer courses that he knows will transfer back to his school. Although he finds the courses just as challenging as at his regular university, he does not worry about his summer grades affecting his 3.2 (out of 4.0) grade point average, because his university only accepts the transfer credits. As long as he receives C grades or better, he maintains his current grade point average. Which theory suggests that the student will work only as hard as necessary to earn a C grade